Datasheet

FILTER FREE OPERATION AND FERRITE BEAD FILTERS
Ferrite
ChipBead
Ferrite
ChipBead
1nF
1nF
OUTP
OUTN
TPA2017D2
www.ti.com ..................................................................................................................................................................................................... SLOS584 – APRIL 2009
A ferrite bead filter can often be used if the design is failing radiated emissions without an LC filter and the
frequency sensitive circuit is greater than 1 MHz. This filter functions well for circuits that just have to pass FCC
and CE because FCC and CE only test radiated emissions greater than 30 MHz. When choosing a ferrite bead,
choose one with high impedance at high frequencies, and low impedance at low frequencies. In addition, select a
ferrite bead with adequate current rating to prevent distortion of the output signal.
Use an LC output filter if there are low frequency ( < 1 MHz) EMI sensitive circuits and/or there are long leads
from amplifier to speaker. Figure 21 shows typical ferrite bead and LC output filters.
Figure 21. Typical Ferrite Bead Filter (Chip bead example: TDK: MPZ1608S221A)
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